YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91...YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91.5 K for the highest value, and the transitionwidth ΔT_c is less than 1 K. The highest magnetization critical current densities J_c achieved 10~6A/cm^2 under 5 T at 10 K and 1.35X10^4 A/cm^2 under 2 T at 70 K (H//c), respectively. The resultscombining the SEM observation indicate that doping of Y211 particles is more effective in improvingthe growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks ofspecimens. Doping of Y_2O_3 powder forms the rod-shaped Y211 particles, but doping of Y211 particlesdirectly to matrix materials forms the spherical Y211 particles mainly. Combining themicrostructures with J_c measurements shows that the interfaces are most important on flux bundlepinning, in which the gradient of free energy is larger than that of other place between the Y211particles and the Y123 matrix materials.展开更多
The study of mechanical properties of high T<sub>C</sub> superconductors is very important for their practical application. A lot of work has been carried out in this field. We have studied the deformation...The study of mechanical properties of high T<sub>C</sub> superconductors is very important for their practical application. A lot of work has been carried out in this field. We have studied the deformation and fracture of bulk YBCO and the effect of doped Ag. The Ag contents dolled in YBa<sub>2</sub>Cu<sub>3</sub>Ag<sub>x</sub>O<sub>7-y</sub> were in a range of X=0 to 1.5. We found that X=0.3 was the optimum Ag content, at which the fracture toughness, hardness and strength increased significantly and reached their maxima. However, the studies on me-展开更多
Fabrication of YBCO superconducting thick films by electrophoresis has been widely reported. However, the value of critical current density (Jc) is far from what the practical application requires. The superconducting...Fabrication of YBCO superconducting thick films by electrophoresis has been widely reported. However, the value of critical current density (Jc) is far from what the practical application requires. The superconducting thick films are obtained using top-seeded melt growth method with different proportional Y2BaCuO5 (Y211) addition. High-pressure oxygen has been used in the annealing process to improve the uniformity of the oxygen content in the superconducting thick films. When 40mol% Y211 powder is added to the YBa2Cu3O7-d (Y123) powder, Jc for the superconducting thick film by approaches described above reaches 7.008?03 A/cm2 (77 K, 0 T), which is greater than the value ever reported.展开更多
One of the major barriers to the application of the bulk high-T_c oxide superconductors is the low value of critical current density J_c caused by the ’weak-link’between grains. To solve the problem, efforts have be...One of the major barriers to the application of the bulk high-T_c oxide superconductors is the low value of critical current density J_c caused by the ’weak-link’between grains. To solve the problem, efforts have been made in cleaning and decreasing the area of grain boundaries as well as in preparing textured materials.展开更多
文摘YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91.5 K for the highest value, and the transitionwidth ΔT_c is less than 1 K. The highest magnetization critical current densities J_c achieved 10~6A/cm^2 under 5 T at 10 K and 1.35X10^4 A/cm^2 under 2 T at 70 K (H//c), respectively. The resultscombining the SEM observation indicate that doping of Y211 particles is more effective in improvingthe growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks ofspecimens. Doping of Y_2O_3 powder forms the rod-shaped Y211 particles, but doping of Y211 particlesdirectly to matrix materials forms the spherical Y211 particles mainly. Combining themicrostructures with J_c measurements shows that the interfaces are most important on flux bundlepinning, in which the gradient of free energy is larger than that of other place between the Y211particles and the Y123 matrix materials.
基金Project supported by the National Center for Research and Development on Superconductivity of China.
文摘The study of mechanical properties of high T<sub>C</sub> superconductors is very important for their practical application. A lot of work has been carried out in this field. We have studied the deformation and fracture of bulk YBCO and the effect of doped Ag. The Ag contents dolled in YBa<sub>2</sub>Cu<sub>3</sub>Ag<sub>x</sub>O<sub>7-y</sub> were in a range of X=0 to 1.5. We found that X=0.3 was the optimum Ag content, at which the fracture toughness, hardness and strength increased significantly and reached their maxima. However, the studies on me-
基金supported the State Key Program of China,the National Natural Science Foundation of China(Grant No.G1999064604)Paper's Foundation Beijing Jiaotong University(Grant No.PD244).
文摘Fabrication of YBCO superconducting thick films by electrophoresis has been widely reported. However, the value of critical current density (Jc) is far from what the practical application requires. The superconducting thick films are obtained using top-seeded melt growth method with different proportional Y2BaCuO5 (Y211) addition. High-pressure oxygen has been used in the annealing process to improve the uniformity of the oxygen content in the superconducting thick films. When 40mol% Y211 powder is added to the YBa2Cu3O7-d (Y123) powder, Jc for the superconducting thick film by approaches described above reaches 7.008?03 A/cm2 (77 K, 0 T), which is greater than the value ever reported.
基金Project supported by Chinese National Center for Research and Development of Superconductivity.
文摘One of the major barriers to the application of the bulk high-T_c oxide superconductors is the low value of critical current density J_c caused by the ’weak-link’between grains. To solve the problem, efforts have been made in cleaning and decreasing the area of grain boundaries as well as in preparing textured materials.
